Process for making di-ammonium phosphate



E. F. PEVERE PROCESS FOR MAKING DI-AMMONIUM PHOSPHATE Filed 001',- 15, 1926 avwe/ntoz W i W Gum/nut! "um "um Dec. 1, 1931.

. Patented Dec. 1, 1931 v v 9;;

E FM nnnnsr r. REVERE, or NIAGARATALLS, nnwyonx; n'ssrsnon, BYJMESNE Assmn- MENTS, o E. I. no PON'I. DE nnmonns & coM'rAuY, on wnzmmerron, nEmAwAnE;

A CORPORATION OF DELAW ARE PROCESS ron MAKING ii -Ammonium rnosrimm" Application'filed October 15, 1926.9Sezia1ito. 141,869.

This invention relates to improvements in processesand apparatus for making di ammonium phosphate.

The invention has for one of its objects.

5 the provision of a novel process and apparatus for making di-ammonium phosphate in such a manner that simplicity of control over .the reactions may be secured so that a the product can be made at alower cost than;

10 heretofore.

A further object of the present invention] resides in a process and apparatus for making the di-ammonium phosphate continu:

are produced, drop out of the mother. liquor solution. Preferably, provision is made for continuously adding both the ammonia and mono-ammonium. phosphate. Accordingly, the di-ammonium phosphate crystals are produced continuously and can be removed continuously as produced in the mother liq.-

1101'. The quantity and concentration of theadded mono-ammonium solution can be so controlled as to just replace the loss of the mother liquor. This loss of mother liquor is occasioned both by the loss due to there'- moval of the crystals and also by the' loss of the mother liquor itself, which is ca-rriedout of the apparatus-with the crystalsfa's they are removed. r I p r Provision is "made for controlling the make-up solution of mono-ammonium phos phate in-a simple manner which provides for a'ready means for so controlling the reaction as to continuously produce a di-salt crystal at'a fixedrate. I 1

,ously' di-ammon continuously.

A" still arther objea 5r theilire sent in'vn tion .resides in the process of continuously. producing di-ammoniumphosphate utilizing mono-ammonium solution. in substantially saturated form at high temperatures and, adding the same to a saturated dia-ammo;v nium phosphate at relatively lower temperatures. Provision is'made fora, temperature;

control of both solutions to' keep thesameat.

the desired temperatures for properly "carry. ing out the re-action. 7 Such, temperature control may be either upon the mother liquor solution orupon the mono-ammonium phosQ phate solution or preferably upon both solid tions, and such temperature control provides a'simple means for effectingthe,re action in. V

a proper manner so asto .produce continue; lum phosphate .in .a compara tively pure state. o v I V j A further featureof the invention resides in theutilization of the cooling effect of. the evaporation and expansion of ammonia used in the process for aiding in maintaininglthe desired low temperature of themother liquor solution. I Y

. Further Ob ects and advantagesf reside in the provlslon of a process and apparatus'for making di-ammonium phosphate continu ously, in which process, recoveries aiemade of all lay-products which are returned to in-'' itial states ofprocessesand again utilized the processes. l

Other objects and advantages willbe here inafter set forth in thetaccompanying-specification and shownin'the drawing5 whichby way of illustrat on shows' in a dlagra'mmatic manner what I now consider as a preferred embodiment of theapparatus used in-c'arr-y ing out-the novel process.

In carrying out the process, assume that: a quantityof saturated mother liquor of diammonium phosphate is in a re-action tank. and that/suitable means are provided for continuously, I removing therefrom di-salt crystals and for havingaimnonia and monoammonium phosphate f solution fed thereto" For a proper re-action, is preferable to keep the mother-liquor solutionatrela-j:

tive low temperatures, say from zero degrees to C. Preferably the temperature range is from 10 to 30 C. The cooling of the mother liquor solution may be secured by a water jacket aided by the cooling eflect of the expanding ammonia used in the process. For a given temperature of the mother liquor solution, the continuous addition of ammonia and substantially concentrated monoammoniui-n phosphate will result the continuous and uniform production of di-ammonium phosphate crystals at a pre-determined rate, providedthe temperature corresponding concentration of the added mono-ammonium phosphate is co ordinated to the desired rate of crystal formation and to. the amount of mother liquor which is removed with the crystals. Such co-ordination of temperature must also take into c onsid eration, the temperature of the mother liquor solution itself. By properly co-ordinating such temperatures, the added ammonia and mono-ammonium phosphate can in this way keep a uniform concentration in the re-action tank itself, affording at all times a saturated i the process both with an equal ratio of solid di-sal't to the mother liquor which is removed with the crystals, and. with varying ratios thereof;

Ratio oi salt to Temperature Concentration Temperature in mother liquor I ot mono-sol of mono-solureaction tank which is reution supply tion per cent moved: tank I by weight The preferred apparatus for carrying out the process will now be described.

In the drawing, 10 indicates a supply tank l or phosphoric acid. A suitable water supply pipe with control valve may be provided as indicated at 11 and P 9, can. beaddedfrom time to time as required. From the tank 10, a pipe 12, provided with a suitable valve leads to a tank or saturator 13 provided with a suitable acket 14. In this saturator, mono-ammonium phosphate is made by admitting ammonia gas to the phosphoric acid solution through a pipe 15. Pipe 15 derives its supply of ammonia gas from an anhydrous ammonia tank 16.. In this supply line there is provided a suitable expansion and control valve designatedat 17. From the saturator 18 in which the mono-ammonium phosphate solution is produced, the solution is admitted when the reaction is complete to a monoammonium supply tank 13a through a suitable valve pipe. In this tank 13a provision is made for controlling the temperature and corresponding concentration. Such control may preferably be secured by means of the valve 14d which controls the medium in the jacket 1%. To facilitate temperature control, a suitable thermometer Ila is provided. From tank 13a substantially concentrated mono-ammonium phosphate is admitted tothe main re-action tank of the apparatus generally designated at 18 through a pipe 19 provided with a control valve 20. It will be understood that valve 20 can be used to control the rate of flow of the mono-ammonium solution to the re-action tank. The re-action tank 18 is provided with a sloping bottom 21 and over this bottom is arranged a traveling belt 22 provid=ed with suitable scrapers. 23 and driven in any convenient manner to scrape the di-salt crystals: which have been formed in the re-action tank from the sloping bottom thereof and dischargethem over an apron 24.. Any convenient means may be provided for driving the traveling belt and it will be understood that. the belt. will remove the crystals continuously and remove with given amounts of crystals, a pro-determined amount of mother liquor which amount will be coordinated with the amount of crystals removed.

In order to control the temperature in the reaction tank a water jacket 26 may be provided. l-Vithin the jacket and preferably,

but not necessarily, disposed below the slop mg bottom 21,. there are provided cooling coils 27and 28 respectively. Cooling coil 27 is. disposed in the ammonia supply line 15 and cooling coil 28 has an open end leading directly into the interior of the re-action tank to discharge ammonia gas thereinto. The flow of ammonia through this coil 28 into the. re-action tank 'ma-y be conveniently controlled by a su'itable'valve 29.

lVith the above arrangement the cooling effect of the evaporation and expansion of annnonia which takes place coils 27 and. 28, can beutilized for maintaining or aiding in maintaining the temperature of the soluppnin tank 18' at the desired low temperature illIHLS.

The temperature of the mother liq-- uor solution may be shown by a suitable thermometer 50. The cooling effect of the ammonia can, if desired be supplemented or reduced by the use of properamounts of cool ing water in jackets :26. For controlling this cooling water, a valve 26acanbe provided. It will be understood that the above apparatus provides for converting the mono-ammonium phosphate solution which is added to the re-ac-tion tank 18, into a di-ammonium solution or mother liquor and for maintaining a proper temperature control so as to cause di-ammonium phosphate crystals to fall out of the solution upon the sloping bottom 21 as the mono-solution is added. This reaction can furthermore be effected without the objectionable ammonia losses heretofore into a centrifuge 30. From this centrifuge the relatively dry crystals are discharged into a steam jacketed vacuum dryer 31 and from time to time the dry crystals can be removed from this dryer. which is thrown out from the crystals by the centrifuge is entrapped and returned to the phosphoric acid tank by means of a pump 33 and return pipe 32. The water vapors and ammonia vapors which are driven off from the crystal dryer, pass through a pipe 34 and condenser 35 and through a trap 36. Condensate is returned to tank 10 by means of a pump disposed in pipe or conduit 38. The uncondensed relatively small amounts of ammonia are withdrawn by a vacuum pump 39 from the trap 36 and are returned to the main supply tank 10 by means ofpipe 40. By the above apparatus, provision is made for expeditiously efiecting the formation of di-ammonium phosphate dry crystals from phosphoric acid and of ammonia. Eifective utilization is made of all waste produced in the process by the apparatus and in this way the cost of carrying out the re-action is materially minimized. All waste productsare returned to the initial steps of the process.

It will be understood that the traveling car rier for the crystals removes these crystals as produced in the reaction tank and also that'the carrier travels at a constant rate of speed. There is, accordingly, a constant rate of removal of the crystals and a corresponding constant rate of removal of the mother liquor from the reaction tank with the' crystals.

WVhat I clalm 1s: 1. A process of producing dl-ammonlum phosphate, which comprises adding ammonia and a hot substantially concentrated solution of mono-ammonium phosphate to a concen-'.

trated solution of di-ammonium phosphate maintained at a relatlvely low temperature. 2.'A process of producing di-ammonium The mother liquor to a concentrated solution ofdi-ammonium phosphate and continuously removing the disalt crystals at a rate co-ordinated to the rate of supply and concentration of the monoammonium phosphate solution and the rate of supply of the ammonia.

3. A method of producing di-ammonium phosphate, which comprises continuously withdrawing di-salt crystals from a concentrated di-ammonium phosphate mother liquor solution, adding continuously to said solution ammonia and substantially concentratedmono ammonium phosphate solution, and coordinating the amount of mono-ammonium solution, and the temperature and concentration thereof, with the amount of di-salt mother liquor which is used and withdrawn in the process. v

4. A method'of producing 'di-ammonium phosphate, which comprises continuously withdrawing di-salt crystals from a concentrated di-ammonium mother liquor solution, adding continuously to said solution ammonia and substantially concentrated mono-ammonium phosphate solution, while maintaining a substantially fixed temperature in the disalt solution and co-ordinating the amount of added mono-solution and ammonia to the amount of mother liquor which is used up.

5; The process of producing di-ammonium phosphate, which comprises forming di-ammonium phosphate crystals, by treating a concentrated solution of di-ammonium phosphate with ammoniaand a solution of monoammonium phosphate, and thereafter drying the crystals and returning diammoniinn' mother liquor removed from the crystals to an initial step of the process.

6. The process of producing.di-ammonium phosphate which comprises adding ammonia gas and mono-ammonium phosphate to a concentrated solut1on of di -ammonium phosphate and in utilizing the cooling effect of the expansion of the ammonia gas for maintainof mono-ammonium phosphate continuously In testimony whereof I hereto aifix my v signature. 

